Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.97	7.167%	$242.1653	$242.17	$242.15	$242.20
Purchase #2	$157.52	4.302%	$164.2965	$164.30	$164.30	$164.30
Purchase #3	$102.86	13.130%	$116.3655	$116.37	$116.35	$116.40
Purchase #4	$47.56	12.123%	$53.3257	$53.33	$53.35	$53.30
Purchase #5	$174.99	12.264%	$196.4508	$196.45	$196.45	$196.50
Purchase #6	$86.93	9.662%	$95.3292	$95.33	$95.35	$95.30
Purchase #7	$92.74	4.502%	$96.9152	$96.92	$96.90	$96.90
7 purchase totals =	$888.57		$964.8482	$964.87	$964.85	$964.90